Fuel cells are used to produce electricity when supplied with fuels containing hydrogen and an oxidant such as air. A typical fuel cell includes an ion conductive electrolyte layer sandwiched between an anode layer and a cathode layer. There are several different types of fuel cells known in the art, one of which is known as a solid oxide fuel cell. A fuel cell is assembled into a fuel cell cassette which provides flow paths for the fuel and the oxidant and provides support for the fuel cell. Multiple fuel cell cassettes are then joined together to produce a fuel cell stack which is capable of producing a desired electrical output.
Fuel cell cassettes must include a seal which provides separation of the fuel and the oxidant. However, fuel cells commonly operate at temperatures in excess of 500° C. which can make it difficult to provide such a seal which is capable of long term operation and which is able to withstand multiple thermal cycles. One known seal is comprised of a silver/copper braze. However, when the silver/copper braze is exposed to the atmosphere experienced in operation of the fuel cell, the silver/copper braze may tend to form porosity which can cause degradation to the sealing capability of the silver/copper braze. Furthermore the silver/copper braze may retain the fuel cell rigidly which may transmit high stresses to the electrolyte layer of the fuel cell and cause durability issues for the fuel cell.
What is needed is a fuel cell cassette which minimizes or eliminates one or more of the shortcomings as set forth above.